The steel wheel track system, or skate wheel track system, is one of the most commonly used flow track systems in the material handling industry. The steel wheel track system comprises a track assembly including one or more parallel track frames. Each track frame includes a pair of parallel steel frame members, also known as “profiles”, and multiple wheel assemblies mounted between the profiles. Each wheel assembly includes a steel wheel rotatably mounted on an axle that extends between the profiles transverse to the track flow direction. The wheels are typically 1.9 inches in diameter and 0.50 inches to 0.56 inches in width. The wheels comprise steel outer shells having thicknesses between 22 gage and 13 gage, depending upon the particular application in which the wheels are used. Additionally, a number of ball bearings are used in the wheels to increase the load capacity of the wheels and to enable the wheels to roll. Each wheel will typically have between six and twelve ball bearings. The load capacity of a skate wheel can vary between twenty-five pounds to one hundred-fifty pounds, depending on the thickness of the shell and the number of bearings the wheel contains.
Steel wheel track systems are predominantly used in picking applications. Picking applications are applications in which a loaded wooden pallet is placed on the track assembly at an entrance end of the track assembly, rolled forward to an exit end of the track assembly and then presented to a picker that takes cartons off the pallet for order picking and shipping to stores or other locations. Steel wheel track systems are also used in applications in which cartons are placed directly on the track assembly and rolled from an entrance end of the track assembly to an exit end of the track assembly.
There are several problems that occur with existing steel wheel track systems. One problem occurs because the pallets used in picking operations are sometimes low quality pallets that have broken bottom boards and/or soft, damaged wood. Due to the narrowness of the steel wheels presently used (only 0.50 inches to 0.56 inches wide), the wheels tend to get caught by broken boards or embed themselves in soft wood. Likewise, when damaged cartons are transported directly on a track assembly, the wheels tend to embed themselves in damaged sections of the cartons. In such situations, a picking operator must pull the pallet or carton towards the exit end of the track assembly using a tool called a shepherd's hook. In doing so, the operator must often exert high forces to keep the pallet moving towards the exit end of the track assembly. As a result, operators have slipped, fallen and sustained injuries while using shepherd's tools to move pallets.
Another problem occurs when low quality pallets are used. When a skate wheel track is designed, consideration is given to the loads that the skate wheels must support. The load that each wheel supports is a factor of the load being carried by the pallets, the length of the pallets used and the number of wheels on the track assembly for a given length (thus, the number of wheels supporting the pallet). Based on the load, the length of the pallets and the number of wheels for a given length, the required load capacity for each wheel can be calculated. A particular wheel design (i.e., outer shell thickness and number of bearings) can be selected. However, the wheels are subjected to unusually high loads when a pallet is used that is missing a front or a back board, or that is otherwise shorter than the pallets the tracking system is designed to carry. This is due to the fact that a fewer number of wheels support the shorter pallet. The wheels may not be capable of supporting the elevated loads and may break, requiring the picking operator to use a shepherd's tool to move the pallets forward along the track assembly. As stated before, this can result in injury to the picking operator.
Yet another problem exists with present steel wheel track systems. Many flow systems, such as those in environments that are subject to FDA cleanliness requirements, require washdowns. However, the steel wheels used in present flow track systems are susceptible to corrosion. Thus, frequent washdowns can damage steel wheels and cap eventually render them inoperable.
It is an object of the present invention to provide a flow track system that will allow pallets and cartons to flow reliably, efficiently, and in a way that is safe for picking operators. It is a further object of the invention to provide a flow track system that can be used in environments that require washdowns.